ART: SHIZUKA AOKI
THE BIG IDEA
HOW TO RE GROW A KIDNEY
More people are waiting for a kidney than
any other organ, but it's one of the hardest
to grow. A transplantable "bioartificial"
kidney is many years away. Here's the
strategy being followed at Wake Forest.
1
Sample
a tiny bit of the
patient's kidney.
2
Sort
kidney tissue
cells from those
of blood vessels
running through it.
3
Multiply
both types of cells
in lab cultures.
4
Inject
the cultured cells
of the patient
into a scaffold,
which is made by
washing a pig
kidney with mild
detergent until
the pig cells are
gone and only the
tough collagen
remains.
5
Incubate
at 98.6°F in a
bioreactor that
delivers oxygen
and nutrients
to the growing
tissue.
Kidney cells
Vessel cells
6
Implant
into the patient
a functioning
human organ
---his own.
8 weeks
later
temperature until the cells form functioning tissue.
The whole process takes six to eight weeks.
Solid organs with lots of blood vessels, such as
kidneys or livers, are harder to grow than hollow
ones like bladders. But Atala's group---which is
working on 22 organs and tissues, including
ears---recently made a functioning piece of human
liver. One tool they use is similar to an ink-jet
printer; it "prints" different types of cells and the
organ scaffold one layer at a time.
Other labs are also racing to make bioartificial
organs. A jawbone has sprouted at Columbia
University and a lung at Yale. At the University
of Minnesota, Doris Taylor has fabricated a
beating rat heart, growing cells from one rat
on a scaffold she made from the heart of
another by washing off its own cells. And at
the University of Michigan, H. David Humes
has created an artificial kidney from cells
seeded onto a synthetic scaffold. The
cell-phone-size kidney has passed tests on
sheep---it's not yet implantable, but it's wear-
able, unlike a dialysis machine, and it does
more than filter toxins from blood. It also makes
hormones and performs other kidney functions.
Growing a copy of a patient's organ may not
always be possible---for instance, when the
original is too damaged by cancer. One solution
for such patients might be a stem cell bank.
Atala's team has shown that stem cells can be
collected without harming human embryos (and
thus without political controversy) from amniotic
fluid in the womb. The researchers have coaxed
those cells into becoming heart, liver, and other
organ cells. A bank of 100,000 stem cell samples,
Atala says, would have enough genetic variety
to match nearly any patient. Surgeons would
order organs grown as needed instead of waiting
for cadavers that might not be a perfect match.
"There are few things as devastating for a surgeon
as knowing you have to replace the tissue and
you're doing something that's not ideal," says
Atala, a urologic surgeon himself. "Wouldn't it be
great if they had their own organ?" Great for the
patient especially, he means.
---Josie Glausiusz